// Copyright (C) 2019-2020 Zilliz. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance
// with the License. You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software distributed under the License
// is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
// or implied. See the License for the specific language governing permissions and limitations under the License

#include "query/ExecPlanNodeVisitor.h"

#include <memory>
#include <utility>

#include "expr/ITypeExpr.h"
#include "query/PlanImpl.h"
#include "query/SubSearchResult.h"
#include "query/Utils.h"
#include "segcore/SegmentGrowing.h"
#include "common/Json.h"
#include "log/Log.h"
#include "plan/PlanNode.h"
#include "exec/Task.h"
#include "segcore/SegmentInterface.h"
#include "common/Tracer.h"
namespace milvus::query {

namespace impl {
// THIS CONTAINS EXTRA BODY FOR VISITOR
// WILL BE USED BY GENERATOR UNDER suvlim/core_gen/
class ExecPlanNodeVisitor : PlanNodeVisitor {
 public:
    ExecPlanNodeVisitor(const segcore::SegmentInterface& segment,
                        Timestamp timestamp,
                        const PlaceholderGroup& placeholder_group)
        : segment_(segment),
          timestamp_(timestamp),
          placeholder_group_(placeholder_group) {
    }

    SearchResult
    get_moved_result(PlanNode& node) {
        assert(!search_result_opt_.has_value());
        node.accept(*this);
        assert(search_result_opt_.has_value());
        auto ret = std::move(search_result_opt_).value();
        search_result_opt_ = std::nullopt;
        return ret;
    }

 private:
    template <typename VectorType>
    void
    VectorVisitorImpl(VectorPlanNode& node);

 private:
    const segcore::SegmentInterface& segment_;
    Timestamp timestamp_;
    const PlaceholderGroup& placeholder_group_;

    SearchResultOpt search_result_opt_;
};
}  // namespace impl

static SearchResult
empty_search_result(int64_t num_queries, SearchInfo& search_info) {
    SearchResult final_result;
    final_result.total_nq_ = num_queries;
    final_result.unity_topK_ = 0;  // no result
    final_result.total_data_cnt_ = 0;
    return final_result;
}

BitsetType
ExecPlanNodeVisitor::ExecuteTask(
    plan::PlanFragment& plan,
    std::shared_ptr<milvus::exec::QueryContext> query_context) {
    LOG_DEBUG("plannode: {}, active_count: {}, timestamp: {}",
              plan.plan_node_->ToString(),
              query_context->get_active_count(),
              query_context->get_query_timestamp());

    auto task =
        milvus::exec::Task::Create(DEFAULT_TASK_ID, plan, 0, query_context);
    int64_t processed_num = 0;
    BitsetType bitset_holder;
    for (;;) {
        auto result = task->Next();
        if (!result) {
            Assert(processed_num == query_context->get_active_count());
            break;
        }
        auto childrens = result->childrens();
        AssertInfo(childrens.size() == 1,
                   "plannode result vector's children size not equal one");
        LOG_DEBUG("output result length:{}", childrens[0]->size());
        if (auto vec = std::dynamic_pointer_cast<ColumnVector>(childrens[0])) {
            processed_num += vec->size();
            BitsetTypeView view(vec->GetRawData(), vec->size());
            bitset_holder.append(view);
        } else {
            PanicInfo(UnexpectedError, "expr return type not matched");
        }
    }
    return bitset_holder;
}

template <typename VectorType>
void
ExecPlanNodeVisitor::VectorVisitorImpl(VectorPlanNode& node) {
    assert(!search_result_opt_.has_value());
    auto segment =
        dynamic_cast<const segcore::SegmentInternalInterface*>(&segment_);
    AssertInfo(segment, "support SegmentSmallIndex Only");

    auto active_count = segment->get_active_count(timestamp_);

    // PreExecute: skip all calculation
    if (active_count == 0) {
        search_result_opt_ = std::move(SearchResult());
        return;
    }

    // Construct plan fragment
    auto plan = plan::PlanFragment(node.plannodes_);

    // Set query context
    auto query_context = std::make_shared<milvus::exec::QueryContext>(
        DEAFULT_QUERY_ID, segment, active_count, timestamp_);
    query_context->set_search_info(node.search_info_);
    query_context->set_placeholder_group(placeholder_group_);

    // Do plan fragment task work
    auto result = ExecuteTask(plan, query_context);

    // Store result
    search_result_opt_ = std::move(query_context->get_search_result());
}

std::unique_ptr<RetrieveResult>
wrap_num_entities(int64_t cnt) {
    auto retrieve_result = std::make_unique<RetrieveResult>();
    DataArray arr;
    arr.set_type(milvus::proto::schema::Int64);
    auto scalar = arr.mutable_scalars();
    scalar->mutable_long_data()->mutable_data()->Add(cnt);
    retrieve_result->field_data_ = {arr};
    retrieve_result->total_data_cnt_ = 0;
    return retrieve_result;
}

void
ExecPlanNodeVisitor::visit(RetrievePlanNode& node) {
    assert(!retrieve_result_opt_.has_value());
    auto segment =
        dynamic_cast<const segcore::SegmentInternalInterface*>(&segment_);
    AssertInfo(segment, "Support SegmentSmallIndex Only");
    RetrieveResult retrieve_result;
    retrieve_result.total_data_cnt_ = 0;

    auto active_count = segment->get_active_count(timestamp_);

    // PreExecute: skip all calculation
    if (active_count == 0 && !node.is_count_) {
        retrieve_result_opt_ = std::move(retrieve_result);
        return;
    }

    if (active_count == 0 && node.is_count_) {
        retrieve_result = *(wrap_num_entities(0));
        retrieve_result_opt_ = std::move(retrieve_result);
        return;
    }

    // Get plan
    auto plan = plan::PlanFragment(node.plannodes_);

    // Set query context
    auto query_context = std::make_shared<milvus::exec::QueryContext>(
        DEAFULT_QUERY_ID, segment, active_count, timestamp_);

    // Do task execution
    auto bitset_holder = ExecuteTask(plan, query_context);

    // Store result
    if (node.is_count_) {
        retrieve_result_opt_ = std::move(query_context->get_retrieve_result());
    } else {
        retrieve_result.total_data_cnt_ = bitset_holder.size();
        tracer::AutoSpan _("Find Limit Pk", tracer::GetRootSpan());
        auto results_pair = segment->find_first(node.limit_, bitset_holder);
        retrieve_result.result_offsets_ = std::move(results_pair.first);
        retrieve_result.has_more_result = results_pair.second;
        retrieve_result_opt_ = std::move(retrieve_result);
    }
}

void
ExecPlanNodeVisitor::visit(FloatVectorANNS& node) {
    VectorVisitorImpl<FloatVector>(node);
}

void
ExecPlanNodeVisitor::visit(BinaryVectorANNS& node) {
    VectorVisitorImpl<BinaryVector>(node);
}

void
ExecPlanNodeVisitor::visit(Float16VectorANNS& node) {
    VectorVisitorImpl<Float16Vector>(node);
}

void
ExecPlanNodeVisitor::visit(BFloat16VectorANNS& node) {
    VectorVisitorImpl<BFloat16Vector>(node);
}

void
ExecPlanNodeVisitor::visit(SparseFloatVectorANNS& node) {
    VectorVisitorImpl<SparseFloatVector>(node);
}

}  // namespace milvus::query